Field of the Invention
The present invention relates to an object detection apparatus for determining whether a detection target is present in an image.
Description of the Background Art
Object detection apparatuses exist for determining whether a target, such as a person, is present in an image captured by a camera, for example. An object detection apparatus may be, together with a camera, mounted on a vehicle, for example. The object detection apparatus determines whether a person is present in an image captured by the camera to notify the driver of the presence of a pedestrian. As a result, the driver of the vehicle can easily recognize the situation outside the vehicle.
To determine whether a target is present in an image, the object detection system uses algorithms with learning functions such as neural networks, support vector machines, and pattern matching. The object detection apparatus defines an area in an input image in which an object is to be detected (referred to as “detection window”). The object detection apparatus uses a program incorporating one of the above algorithms to determine whether a target is present in the detection window.
For example, the image recognition apparatus of Patent Document 1 defines a plurality of detection windows that partially overlap, and uses a reference pattern of a target to be recognized (for example, a pedestrian) to perform pattern matching on each detection window. For a region for which pattern matching is performed more than once, the image recognition apparatus integrates the pattern matching results. Based on the results of integration, the image recognition apparatus identifies the location of the pedestrian.
Patent Document 2 describes a position detection apparatus for detecting the position of the license plate of an automobile based on an image, using a neural network. The position detection apparatus cuts out a small area from an original image captured by a camera and applies the neural network to this small area. The output values of the neural network are converted in scale to the size of the small area. The position detection apparatus multiplies the output values from scale conversion by a Gaussian window to generate, for each of small areas, a projected image that reflects the output values. Based on an image obtained by summing the projected images for the small areas, the position detection apparatus identifies the position of the license plate.